280 
to the abundance of adults. Our collections, extending over longer 
periods and being at briefer intervals, indicate, however, that this 
relation does exist. As above stated, the larve are most abundant 
at or shortly after the times of greatest abundance of adults—that 
is, the maxima of the recurrent pulses. Apstein also states that 
reproduction is periodic and development rapid. Maximum 
numbers are reported by him in May and September. 
Cohn (’03), on the other hand, maintains that the “innere Logik” 
and his data show him that the naupliu reach their greatest numbers 
just prior to the appearance of largest numbers of young and adult 
Copepoda. His data are from 12 collections between May 1 and 
October 1, and favor his contention in 2 out of 3 cases (of maxima), 
and both of these le in collections at intervals of 15 to 16 days. In 
the light of our data obtained at briefer intervals and the conclusions 
therefrom that the pulses of larvae tend to coincide or follow at a 
brief interval those of the adults, it becomes questionable whether 
his data are sufficient for his conclusion. His logic also overlooks 
the fact, apparently, that'smaller numbers of larve might lead to 
coincident maxima of grown forms during a period of abundant 
food, on which all pulses must be based, since the larval stage may 
be at such times a brief one and the adult a relatively longer one, and 
the cumulative effect of this relationship would make the conditions 
shown in our data logically possible. Furthermore, Cohn used a 
No. 12 silk in his plankton net, and this allows many nauplu to 
escape, and probably accounts for the fact that the ratio of larvee 
to grown forms in his figures is only 1.3 to 1, while in our records it 
is 3.5 to 1. The discrepancy arising from this leakage may further 
tend to weaken his data for his conclusions concerning the relations 
of larvee and adults. 
Steuer (’01) finds that the nauplii-in the Danube at Vienna 
reach maxima in June and in August, but his data are too scattered 
to fully delineate their fluctuations. Two out of three of his max- 
ima coincide with those of all Cyclops, and the third antedates it 
(monthly intervals of collection), as in Cohn’s data. 
Diaptomus pallidus Herrick.—Average number per m.’, 11; in 
1897. 367> in 1896.°87- san 1895152 Said in 1894, 146. 
This species was recorded in all months cf the vear but February, 
though in a larger percentage of the collections and in larger numbers 
in July-December. Prior to this season the percentage does not 
